1. Field of the Invention
The invention is related to an automatic delivery device for lubricating a bearing, comprising an oil inlet and an oil outlet opening as well as a side channel pump with preferably planar delivery blades.
2. Description of Background and Material Information
A great number of different systems are available for lubricating machine bearings. A method often used for bearing lubrication of large machines is low pressure circulation lubrication. In this connection, oil is conveyed by means of a pump from an oil tank into an elevated reservoir, with the interposition of a cooling device and a filter (or cooling and filtering unit). From there the oil flows to the bearings to be lubricated under the force of gravity. This type of lubrication is very efficient and also economical, because the circulating oil is run through a filter and therefore can be used over again for some time.
This system has nevertheless several disadvantages which have proven to be very serious, in particular in connection with installations of great importance.
In connection with important installations in which the mentioned system is used, two oil pumps are customarily provided so as to be able to switch to the other pump if one of them should fail. To increase reliability further, it is possible to supply each one of these pumps from a different electrical system. Normally, one of these pumps is driven by an AC motor, the other with a DC motor, the DC current mostly being drawn from a battery-equipped emergency supply system. There obviously is a danger of both electrical systems failing or both motors or both pumps becoming damaged within a short period of time. In such cases the machine to be lubricated must naturally be shut down. Even with an appropriate optimal layout of the elevated reservoir, oil supply will only be available for a short time, usual times being approximately five to ten minutes.
A further disadvantage consists in that first the elevated reservoir must be filled with oil before the machine to be lubricated can be permitted to be started. In connection with some bearing designs, starting of the machine is also delayed because the bearings first must be filled with oil.
Not only is the elevated reservoir placed higher than the machine to be lubricated, often it is housed in another room located above it. In practice, difficulties often arise from the discrepancy between the space required and the space actually available. A further weak point often is constituted by the three pipes leading to the elevated reservoir, i.e., the supply, run-off and relief pipes. Not only do they often require valuable space, but quite often it is very difficult to lay them without creating dead corners and zones of heating.
A low-cost self-contained lubricating system for a bearing of a turbine shaft seated in the support housing is presented in U.S. Pat. No. 4,605,101, issued on Aug. 12, 1986. This lubricating system consists of a first seal arrangement between the shaft and housing, positioned at an axial distance from one side of the bearing arrangement, and a second seal arrangement between the shaft and housing, positioned at an axial distance from the other side of the bearing arrangement. The bearing arrangement is embodied in such a way that an oil sump chamber which contains the lubricant is created in the support housing. Each bearing arrangement contains an elastic O-ring between the shaft and the support housing as well as two impeller wheels which are connected inside the oil sump chamber with the shaft and pump the lubricant from the oil sump chamber through the bearing arrangement and back to the oil sump chamber during the rotation of the shaft.
Even though the lubricating system proposed in U.S. Pat. No. 4,605,101 is of low cost, it has the disadvantage that the lubricant must often be renewed, which requires interruptions of the operation.
In United Kingdom Patent No. 1,238,199, published on Jul. 7, 1971, a roller bearing arrangement is described, which includes in particular a fast-moving shaft roller bearing. A roller bearing is used having an inner and an outer bearing race as well as a roller cage with associated rollers. In accordance with the main claim of the aforementioned United Kingdom patent, means are provided which become effective with the rotation of the bearing and cause hydraulic coupling of the roller cage. In accordance with the dependent claims of the aforementioned United Kingdom patent, several such means are proposed, oil or an oil-air mixture being cited in one of the claims. The bearing is definitely rigidly mounted on the shaft in this case, where the medium transferring the torque from the shaft to the roller cage is a lubricating oil or an oil-air mixture. This lubricating and transmission medium is transported to the bearing cage through conduits in the shaft and the inner bearing race. Oil outlet conduits are provided on both sides in the outer bearing race. By means of this, the lubricating and transmission medium can run off without delaying the roller movement.
The purpose of the invention in United Kingdom Pat. No. 1,238,199 is not primarily lubrication of a bearing, but the improvement of the kinematic running conditions of the rollers when the shaft is pre-stressed. The disadvantage is that with heavy, jerky operation, the constant lubrication of the rollers is not assured.
German Published Patent Application No. 3,343,593, published on Jun. 13, 1985, deals with the lubrication of a rolling bearing of large diameter. Its definite purpose is the improvement of the known lubrication system of fastturning roller bearings, the balls or rollers of which do not come in contact with an oil bath and are therefore lubricated by means of whirling upwards. It is proposed in the aforementioned German publication to embody the portion of the whirling disks which dips into the oil bath and is fixedly connected with the rotating portion of the bearing in the form of an axially extending collar. The whirling disk is closely surrounded by a chamber which is open to the top in the direction of the roller bearing. The oil film is pushed in the direction of the roller bearing in this area.
The disadvantage of the invention of the aforementioned German publication lies in that the constant supply of amounts of oil to the bearing cannot be assured, because of which operational disruptions can occur in machines with extremely high rpm.